This invention relates to a power assembly, or xe2x80x9cgear boxxe2x80x9d, for supplying rotary power at a selected speed. More specifically, the assembly provides for the changing of a worm drive to alter the speed at which the assembly delivers. This is accomplished by changing the diameter of the worm gear and the distance between the driving worm and the axis of the worm gear.
In the past worm-gear-type gearboxes have required a major restructuring to change the speed range. Basically, the restructuring has been in consequence of changing the diameter of the worm gear. Restructuring has involved a changing of the center distances between the worm gear and the worm and has usually involved the manufacture of a new housing, an expensive proposition. There has been a need for a simpler route which can be flexible and reversible, allowing changes to be readily made without major restructuring.
In the present invention the worm gear may be changed and the center distances changed without the need to manufacture a new housing. The invention is a power assembly comprising opposed aligned upper and lower housing portions, each being of open-box shape having a bottom wall and side walls to comprise a closed housing having spaced parallel top and bottom walls. One of said upper and lower housing portions rotatably mounts a worm gear having a fixed axis. A frame is disposed in the housing between and parallel to the top and bottom walls secured at a selected height relative to the worm gear, the frame mounting a worm on a fixed axis and meshing with the worm gear, and a motor on the frame operatively driving the worm.
With the structure thus described, it is possible to change the worm gear and move the frame carrying the worm closer or farther away from the worm gear axis so that the worm gear and the worm mesh properly.